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Anti-Streptolysin-O Test (Streptococcal-Antibody Test)
Anti-Streptolysin-O Test (Streptococcal-Antibody Test)
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Anti-Streptolysin-O Test (Streptococcal-Antibody Test)
Category: Immune response.
Subcategory: Viral, bacterial and fungal tests.
Material studied: Blood.
Estimated cost of test: $25.00.
Patient time for test: 5-10 minutes.
Reliability of test results: Good.
Available as home self-test? No.
Note: Test detects the body's immunologic response to streptococcal bacteria.
BEFORE THE TEST
Purpose of test:
Confirms recent or ongoing streptococci infection.
Helps diagnose rheumatic fever* and post-streptococcal glomerulonephritis* in the presence of clinical symptoms.
Distinguishes between rheumatic fever* and rheumatoid arthritis* when joint pain is present.
In some cases, test is repeated at regular intervals to identify active and inactive states of rheumatic fever* or to confirm acute glomerulonephritis*.
Where is test performed?
Commercial laboratory, hospital, doctor's office.
Who performs test?
Lab technician, nurse, doctor.
Risks and precautions:
If tourniquet is applied on the arm too long (over 1 minute), it may cause an inaccurate test result. Request another sample to be collected to ensure accuracy.
Patient preparation:
Activity--No changes necessary.
Diet--No changes necessary.
Medicines--Inform the person performing the test if you have recently taken any medications listed under Taking these drugs may affect test results. You may be asked not to take this medication before the test.
Disrobing--None required. Roll up sleeve only.
THE TEST
Sensory factors:
Touching--You will feel mild discomfort when the needle is inserted into the vein or when the lancet pricks a finger, heel or ear lobe.
Seeing--You will see the technician, nurse or doctor, the basket or tray to hold the equipment, the needles, syringes, collecting tubes and bandages.
Feeling--Some degree of apprehension or fear is normal and should be expected. Discomfort disappears when the test is finished.
Other senses (taste, smell, hearing)--Not affected.
Equipment used:
Needles, syringes and heparinized* collecting tubes. Sterile, disposable equipment prevents contamination or spread of infection. There is no risk of becoming infected with the hepatitis virus, AIDS virus or any other infecting germ.
Description of test:
Technician, doctor or nurse applies a tourniquet or blood-pressure cuff to the upper arm if blood is collected from a vein.
Skin over the vein to be stuck is cleaned with alcohol or other antiseptic on a piece of cotton.
When blood is drawn from a vein, the operator feels the vein to be used then punctures both the skin and vein in one quick stroke. The needle used is a sterile, disposable needle attached to a sterile, disposable syringe.
Operator withdraws the needle and transfers sample from the collecting syringe into sterile tubes (identified with your name) before sending samples to the laboratory for analysis. Tubes are treated with an anti-coagulant chemical to prevent clotting.
If blood is collected from a finger, heel or ear lobe, skin over the selected site is cleaned with an antiseptic. The operator quickly pierces the skin to a shallow depth, using a sterile, disposable metal lancet. The drop or two of blood produced is collected into a capillary pipette.
AFTER THE TEST
Immediate post-test care:
Apply pressure to the puncture site with cotton provided by the laboratory.
If a vein has been punctured, raise your entire arm over your head while applying pressure.
Some discoloration, soreness or swelling may develop at the venepuncture site. This responds well to moist, warm compresses applied every 2 to 4 hours.
Activity after test:
Resume taking any medications that were withheld before the test.
Return to pretest activities right away.
Use warm compresses if blood collects under the puncture site or if the area becomes tender, red or painful.
Time before test results available: Test requires only a few minutes in the laboratory. Time before results are reported to the doctor or patient varies from a few minutes to a few days.
TEST RESULTS
Test values:
Test results are determined by agglutination* test.
Normal values:
Even healthy people have some detectable ASO titer* from previous minor streptococcal infections.
Adults--ASO titer* less than 85 Todd units/ml.
School-age children--ASO titer* less than 170 Todd units/ml.
Preschoolers--ASO titer* less than 85 Todd units/ml.
What HIGH or INCREASED ASO titers* may indicate:
Prolonged or recurrent streptococcal infections.
Inactive rheumatic fever*.
Probable acute rheumatic fever* or acute post-streptococcal glomerulonephritis*.
Post-streptococcal disease*.
Taking these drugs may affect test results:
Antibiotics.
Corticosteroids.
Other factors that may affect test results: If you have streptococcal skin infections, false-negative results can occur, even if you have post-streptococcal disease*.
*See Glossary.
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